The Expression of IV6β[ Gal β1–4(Fucα1–3)GlcNAc]-Gb5Cer in Mouse Kidney Is Controlled by the Gsl-5 Gene through Regulation of UDP-GlcNAc:Gb5Cer β1–6N-Acetylglucosaminyltransferase Activity1

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Abstract
We reported the polymorphic expression of GL-Y (IV6β[Galβ1-4(Fucα1-3)GlcNAc]-Gb5-Cer in kidneys of inbred strains of mice in previous papers [J. Biochem. 101, 553–562 and 563–568 (1987)]. DBA/2 mice express a large amount of GL-X (Gb5Cer), but not GL-Y, in their kidneys, because of a defect on a single autosomal gene (Gsl-5). This suggested that DBA/2 mice lack the ability to transfer GlcNAc onto the C-6 position of GalNAc of Gb5Cer or GL-X. In this study, we characterized UDP-GlcNAc:GL-X β1-6N-acetylglucosaminyl-transferase (β1-6GlcNAc transferase) in the microsomal fraction of mouse kidney. Maximum activity was detected with an incubation mixture containing sodium cacodylate buffer (pH 6.4), 0.1% Zwittergent 3–16 and 1 mM EDTA. Divalent cations were not required. The apparent Km values for UDP-GlcNAc and GL-X were 0.42 and 0.12 mM, respectively. The product of the enzymatic reaction was identified as IV6/9GlcNAc-Gb5Cer by means of 1H-NMR spectroscopy and permethylation analyses. Then, we measured the β1-6GlcNAc transferase activity in the microsomal fractions of kidneys of inbred strains of mice and progeny obtained on mating. WHT/Ht, C57BL/10, BALB/c, and C3H/He mice, which express GL-Y in their kidneys, exhibited detectable amounts of activity, whereas CBA and DBA/2 mice, which do not express GL-Y, did not exhibit detectable activity. Analyses of the glycolipid expression and β1-6GlcNAc transferase activity in the kidneys of backcross mice obtained on mating between (WHT/Ht×DBA/2)F1 and DBA/2 mice indicated that the expression of GL-Y essentially requires the expression of the transferase activity. Thus, we conclude that G8l-5 controls the expression of GL-Y through regulation of the β1-6GlcNAc transferase activity, and consequently DBA/2 mice cannot express IV6/βGlcNAc-Gb5Cer and IV6β(Galβ1-4GlcNAc)-Gb5Cer either.

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